There has been a considerable effort to remove lead and other toxic materials from the environment, particularly from children's rooms and toys. In carrying out this effort, it is desirable to provide lighting circuits for shoes and other garments that are solder and lead (Pb) free. Circuits that are concealed in shoes are usually glued or cemented into the heels and are generally inaccessible; but as these shoes find their way into landfills, the toxic lead can possibly leach out, contaminating the environment.
There is also concern about solder joints in hand sets (cell phones) televisions, computers and related electronic gear, especially consumer items that may also find their way into landfills. Considerable work has been done in trying to eliminate solder and solder joints containing lead. Some have attempted to use tin (Sn) solder for solder joints, but it has been found that pure tin solder in small, fine circuits tends to grow projections called “dendrites”, also called “tin whiskers”, that cause circuit failure such as short circuits. This problem is cured with a small percentage of lead in the solder, but this is obviously an unsatisfactory solution.
My earlier effort in the application Ser. No. 10/773,647 was directed toward complete elimination of solder and included a lead (Pb) free circuit including a printed circuit board having conductor tracks on its surface with components having conductive pads contacting the conductive tracks. The components are covered with a layer of foam material, which, in turn, is covered by a clamping plate consisting of a sheet of hard material that is compressed against the foam to force the conductive pads of the surface mount components firmly against the conductor tracks. This assembly was screwed together by means of bolts and nuts. All or part of the described circuit may be covered with potting compound.
Impact or motion responsive switches are commonly associated with such electronic circuits or modules in clothing or footwear. Examples are illustrated by the following U.S. Patents of this inventor:
Re 37,2205,692,3246,238,0565,649,7556,017,1285,366,7805,732,4865,285,5865,704,706and 5,019,438The circuit or module components are normally soldered in place and may be a source of lead contamination whenever the garments or footwear are discarded and find their way into waste disposal areas.